I haven't experienced it with my LPF flippers, but my cannon plunger was doing something similar and getting stuck in the open position (plunger extended). Turns out is was a loose screw backing out of the mounting bracket that the plunger was coming in contact with. I missed it the first time I looked because it was hidden by the plunger. Hopefully your situation is something just as simple...

Could it be the coil stop is magnetized? Try replacing the coil stop or if you don't have one, try a little electrical tape on it just to see if that's the problem.

No problem. That was more just to identify the issue. But now that you know what it is, even though it's not a permanent fix it should be easy enough to fix and you can play it until you do.

I read somewhere a while ago that if you tap (bang) metal parts against the side of the wood then that can de-magnitze them. It might be an old wives tale, but maybe try that with the stop and the plunger. Maybe that'll demagnetize it.

Or maybe another piece of wood that's not the side of your AC/DC.

Otherwise, I guess it can't hurt to leave the tape, but I assume sooner or later it will wear.